1. Field of the Invention
The present invention relates to a liquid-droplet jetting apparatus which jets liquid droplets, and a method of recovering a liquid-droplet jetting head.
2. Description of the Related Art
As an ink-jet printer which jets ink to a recording paper or the like, a so-called line-type ink-jet printer is known, which has a plurality of nozzles arranged in a direction (primary scanning direction) orthogonal to a feeding direction (secondary scanning direction) of this recording paper or the like. This line-type ink-jet head has an advantage that the line-type ink-jet head performs recording faster than a serial-type ink-jet head because the line-type ink-jet head is capable of recording by jetting ink from nozzles arranged in a line entirely across the width of the recording paper. On the other hand, since the line-type ink-jet head has a large number of nozzles, when dust, air and/or the like enter in any of the nozzles, jetting abnormality or failure easily occurs, in the line-type ink-jet head, such as that the liquid droplet cannot be jetted (misfiring or non-discharge of liquid droplet); a liquid droplet of the ink is jetted in a direction deviated or bent from an intended jetting direction (bending in the jetting direction), which in turn causes the liquid droplet land on a position deviated from an intended landing position; and the like. When such a jetting abnormality occurs, a while streak or line is formed in a recorded letter or image, thereby degrading the printing quality.
In this case, if a nozzle having jetting abnormality (nozzle at which jetting abnormality occurs, abnormal nozzle) can be identified, it becomes possible to purge only the nozzle, or to complement or compensate for (jet ink instead of) the failed or abnormal nozzle by a normal nozzle of another head, which enables efficient elimination of the jetting abnormality.
For example, Japanese Patent Application Laid-open No. 11-334047 discloses a line-type ink-jet printer having a nozzle checking means for detecting a nozzle in an abnormal jetting state. The nozzle checking means is constituted of a laser light source and a light-receiving element provided at both ends, respectively, of the ink-jet head. Then, liquid droplets are jetted sequentially from a plurality of nozzles in a state that laser light is emitted in parallel to a direction in which the nozzles are arranged (nozzle arrangement direction). When liquid droplets are jetted normally from the nozzles, the laser light is blocked by the liquid droplets, but when liquid droplets are not jetted from the nozzles, or when bending in the jetting direction occurs, the laser light is not blocked by the liquid droplets, so that the nozzle having jetting abnormality can be identified.
Incidentally, in the line-type ink-jet head, bending of the jetting direction (displacement or deviation from landing position) of liquid droplets in the arrangement direction of nozzles, which is orthogonal to the feeding direction of a recording paper, generates a white line or streak on a recording paper in parallel to the feeding direction for the recording paper, which can significantly affect the printing quality as compared to bending of the jetting direction with respect to the paper feeding direction. However, in the ink-jet printer disclosed in the Japanese Patent Application Laid-open No. 11-334047, since the laser light is emitted from the laser light source in parallel to the arrangement direction of the nozzles, it is not possible to detect bending of the jetting direction with respect to the arrangement direction of the nozzles.
In view of the above situation, when an attempt is made to emit laser light in parallel to the paper feeding direction to each of all the arranged nozzles so as to detect bending of the jetting direction in the arrangement direction of the nozzles, it is necessary to provide the nozzle check means constructed of the laser light source and the light-receiving element for each of the nozzles. As a result, the structure becomes large and the costs of parts increase.